The present disclosure relates to a dielectric film, a method of manufacturing the same, and a semiconductor capacitor having the dielectric film, and more particularly, to a dielectric film having a ferroelectric layer, a method of manufacturing the same, and a semiconductor capacitor having the dielectric film.
Pb-containing perovskite compounds exhibit good dielectric, ferroelectric, piezoelectric, and optoelectric properties. Pb-containing perovskite compounds are widely used in ferroelectric random access memories (FRAMs), piezo-resistive sensors, actuators, integrated optical devices, etc.
One of typical perovskite compounds is Pb(Zr,Ti)O3 (PZT) that has a higher electromechanical coupling coefficient than BaTiO3 and also has a good temperature stability over a wide temperature range. Pb(Zr,Ti)O3 layers must be at least approximately 2,000 Å in thickness so as to ensure a high remanent polarization, a high drivability, a high dielectric breakdown voltage, a high coercive voltage, and a durability against external environment.
As most of electromechanical devices as well as memories are further miniaturized, Pb(Zr,Ti)O3 layers are required to be thin while ensuring good dielectric characteristics. Thin Pb(Zr,Ti)O3 layers, however, cannot ensure a high remanent polarization, a high drivability, a high dielectric breakdown voltage, a high coercive voltage, and a durability against external environment. Consequently, desired device characteristics cannot be obtained.
When a ferroelectric layer having a thickness greater than 2,000 Å is interposed as a dielectric film between two electrodes of the semiconductor capacitor, it is difficult to obtain a desired capacitance of the semiconductor capacitor because the capacitance of the semiconductor capacitor is in inverse proportion to the thickness of the dielectric film.
Therefore, the perovskite ferroelectric layer such as the Pb(Zr,Ti)O3 layer has a trade-off relationship between the dielectric characteristic and the capacitance of the semiconductor capacitor. Hence, it is difficult to satisfy both of the dielectric characteristic and the capacitance of the semiconductor capacitor.
In micro-electromechanical systems (MEMS), the ferroelectric layer works as the key functional layer due to its higher piezoelectric coefficient compared to that of other piezoelectric materials, such as ZnO or GaN, where the piezoelectric properties are used to convert the electrical signal to the mechanical movements. In order to realize this, the ferroelectric layer usually should be poled into one poling direction by application of a proper electric voltage. By this poling, the ferroelectric layer has a uniform ferroelectric domain distribution and shows the proper electromechanical behaviors. During its normal service, the repeated electrical signal might depole the ferroelectric layer and its functionality becomes degraded. In order to suppress these deleterious effects, the ferroelectric layer should have a high remanent polarization and high coercive voltage. Conventionally, these purposes have been achieved by either increasing the ferroelectric layer thickness or increasing process temperature which both impose several problems in fabricating the MEMS devices. In addition, the usual ferroelectric layers have lower polarization when the coercive voltage is high and vice versa.